86-DOS Version 0.34-C
Serial #221
Copyright 1980 by Seattle Computer Products
This
is the precursor to MS-DOS and is likely the 2nd oldest known version to
survive.
[Update 31Dec23]
This disk can be booted via the SIMH emulator. Instructions can be found here:
https://web.archive.org/web/20181002215506/http://www.86dos.org/index.htm